JP7741971B2 - Battery control device and battery control method - Google Patents

Description

The present invention relates to a battery control device and a battery control method.

In order to maximize battery performance, electric vehicle systems installed in electric vehicles such as electric vehicles (EVs), plug-in hybrid vehicles (PHEVs), and hybrid vehicles (HEVs) are equipped with a battery control device that detects battery voltage, temperature, and current and, based on these, calculates the battery's state of charge (SOC), state of health (SOH), and the battery's available input and output power (hereinafter referred to as available input and output power).

The battery's input and output power is calculated using the battery's upper or lower voltage limit and the battery's internal resistance as the maximum power that can be input and output within the range in which the battery voltage does not deviate from the upper or lower voltage limits. By controlling the battery voltage within the range in which it does not deviate from the upper or lower voltage limits, it is possible to avoid use in high current ranges where the battery voltage changes sharply, and to suppress battery degradation.

The reason battery voltage changes abruptly in the high-current region is that, for example, when a typical lithium-ion battery is used as a secondary battery, a lithium ion concentration gradient occurs in the diffusion layer formed near the interface between the electrode and electrolyte, requiring a large overvoltage to supply lithium ions from the electrolyte to the electrode when a large current is passing through. Therefore, to avoid using the battery in the high-current region, it is desirable for the battery control device to appropriately set the upper current limit value in accordance with the lithium ion concentration gradient in the diffusion layer near the interface between the electrode and electrolyte, which changes variously with charging and discharging.

The technology described in Patent Document 1 is known regarding a method for limiting the current of a secondary battery that takes into account the ion concentration of the electrolyte.

JP 2013-137935 A

Conventional technologies, such as those described in Patent Document 1, do not take into account the ion concentration gradient in the diffusion layer formed near the interface between the electrode and the electrolyte, and therefore are unable to set an upper limit current value that takes into account the sudden changes in battery voltage in the high current region described above.

For example, during continuous high-current charging or discharging, the internal resistance increases as the lithium ions near the battery electrodes decrease, but it is difficult to accurately model this behavior. When a battery is charged or discharged in a range that cannot be reproduced by a voltage equivalent circuit model, calculation errors occur in the battery's internal resistance. As a result, the available input/output power cannot be calculated accurately, and even if the battery is charged or discharged according to the available input/output power, the battery voltage may deviate from the upper or lower voltage limits.

The object of the present invention is to improve the calculation accuracy of the battery's available input and output power.

In order to solve the above problem, the present invention is characterized by comprising a correction coefficient calculation unit that calculates a correction coefficient based on the discrepancy between the state of the secondary battery determined from measured values related to the secondary battery and the state of the secondary battery calculated using a model related to the secondary battery, and a power limit value calculation unit that calculates a value related to the power that can be input and output to the secondary battery by applying correction using the correction coefficient.

According to the present invention, the battery's available input and output power can be accurately determined.

1 is a block diagram showing the configuration of an electric power system of a hybrid vehicle according to a first embodiment of the present invention; FIG. 2 is a block diagram showing the configuration of a cell control unit that constitutes the battery system of FIG. 1 . FIG. 2 is a block diagram showing the configuration of a battery pack control unit that constitutes the battery system of FIG. 1 . Diagram explaining the data table showing the relationship between SOC and OCV FIG. 1 is a block diagram showing the configuration of an SOC calculation unit that constitutes a battery pack control unit in the first embodiment. Diagram explaining how to calculate SOC from OCV FIG. 1 is a block diagram showing the configuration of a SOH calculation unit that constitutes a battery pack control unit in the first embodiment. FIG. 1 is a block diagram showing the configuration of a power limit value calculation unit that constitutes a battery pack control unit in the first embodiment. A diagram showing an example of an equivalent circuit model of a battery Diagram explaining the voltage behavior of a battery Voltage behavior when internal resistance increases due to lithium ion diffusion FIG. 1 is a block diagram showing the configuration of a power limit value calculation unit according to the first embodiment of the present invention. Power, current, and voltage waveforms when power equivalent to the output power available before the application of the invention described in Example 1 is input to the battery Power, current, and voltage waveforms when power equivalent to the outputtable power when the invention described in Example 1 is applied is input to the battery FIG. 10 is a block diagram showing the configuration of a battery pack control unit that configures the battery system of FIG. 1 in a second embodiment. FIG. 10 is a block diagram showing the configuration of a power limit value calculation unit in the invention described in Example 2. Schematic diagram of a battery pack consisting of cells with different internal resistance values connected in series Power, current, and voltage waveforms when power equivalent to the output power available before the application of the invention described in Example 2 is input to the battery Power, current, and voltage waveforms when power equivalent to the inputtable power before the application of the invention described in Example 2 is input to the battery Power, current, and voltage waveforms when power equivalent to the outputtable power when the invention described in Example 2 is applied is input to the battery Power, current, and voltage waveforms when power equivalent to the inputtable power when the invention described in Example 2 is applied is input to the battery FIG. 10 is a block diagram showing the configuration of a power limit value calculation unit in the invention described in Example 3. FIG. 10 is a diagram showing the power limit coefficient in the invention described in Example 3. Power, current, and voltage waveforms when power equivalent to the outputtable power when the invention described in Example 3 is applied is input to the battery Power, current, and voltage waveforms when power equivalent to the inputtable power when the invention described in Example 3 is applied is input to the battery FIG. 10 is a block diagram showing the configuration of a battery pack control unit that configures the battery system of FIG. 1 in a fourth embodiment. FIG. 10 is a block diagram showing the configuration of a SOH calculation unit that constitutes a battery pack control unit in a fourth embodiment. FIG. 10 is a block diagram showing the configuration of a power limit value calculation unit in the invention described in Example 4. FIG. 10 is a diagram showing waveforms of current, voltage, SOH, correction coefficient kchg, and maximum output power Pmax_d during pulse current input before the invention described in Example 4 is applied. FIG. 10 shows waveforms of current, voltage, SOH, correction coefficient kchg, and maximum output power Pmax_d during pulse current input after application of the invention described in Example 4.

An embodiment of the present invention will be described based on the drawings.

In the embodiment described below, we will explain the application to an energy storage device that forms the power source for a hybrid electric vehicle (HEV).

The configuration of the embodiment described below can also be applied to a storage battery control circuit of a storage device that forms the power source for passenger cars such as plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs), and industrial vehicles such as hybrid railway vehicles.

In the following examples, we will use lithium-ion batteries as the capacitors that make up the power storage unit. Other types of capacitors that can be used include nickel-metal hydride batteries, lead batteries, electric double-layer capacitors, and hybrid capacitors.

The first embodiment of the present invention will be described based on Figures 1 to 14.

Figure 1 shows an example configuration of an electric system for a hybrid vehicle in this embodiment. The electric system in this embodiment is connected to a battery 100, an inverter 400, and a motor 410 via relays 300 and 310. A vehicle control unit 200 determines the distribution of driving force, etc., based on information including the SOC of the battery 100, information from the inverter 400 and motor 410, and information from the engine (not shown).

The configuration of the battery 100 will be described. The battery 100 has a battery pack 110, a cell management unit 120, a current detection unit 130, a voltage detection unit 140, a battery pack control unit 150, and a memory unit 180. The battery pack 110 is composed of multiple cells 111. The cell management unit 120 monitors the status of the cells 111. The current detection unit 130 detects the current flowing through the battery 100. The voltage detection unit 140 detects the total voltage of the battery pack 110. The battery pack control unit 150 controls the battery pack 110. The memory unit 180 stores information regarding the battery characteristics of the battery pack 110, the cells 111, and the cell group 112. The battery pack control unit 150 receives the battery voltage and temperature of the cells 111, the current flowing through the battery, the total voltage of the battery pack 110, diagnostic results for the cells 111, and abnormality signals. The battery voltage and temperature of the battery 111 are transmitted from the battery management unit 120. The current value flowing through the battery is transmitted from the current detection unit 130. The total voltage value of the battery pack 110 is transmitted from the voltage detection unit 140. The diagnosis result of the battery 111 indicates whether it is overcharged or overdischarged. An abnormality signal is output when a communication error occurs in the battery management unit 120. The battery pack control unit 150 detects the state of the battery pack 110 based on the input information. The results of processing performed by the battery pack control unit 150 are transmitted to the battery management unit 120 and the vehicle control unit 200.

The battery pack 110 is composed of multiple cells 111 (lithium ion batteries) electrically connected in series, each capable of storing and discharging electrical energy (charging and discharging DC power). The output voltage of each cell 111 is 3.0 to 4.2 V (average output voltage: 3.6 V), and the OCV and SOC of each cell 111 are assumed to have the correlation shown in Figure 6. However, other voltage specifications are also acceptable.

The cells 111 that make up the battery pack 110 are grouped into a predetermined number of units for status management and control. The grouped cells 111 are electrically connected in series to form a cell group 112. The predetermined number of units may be equal, for example, 1, 4, 6, etc., or may be a composite number, such as a combination of 4 and 6.

The cell management unit 120, which monitors the status of the cells 111 that make up the battery pack 110, is composed of multiple cell control units 121, with one cell control unit 121 assigned to each of the cell groups 112 grouped as described above. The cell control unit 121 operates by receiving power from the assigned cell group 112 and monitors the battery voltage and temperature of the cells 111 that make up the cell group 112. In FIG. 1, cell control units 121a and 121b are provided corresponding to cell groups 112a and 112b. In this embodiment, for simplicity, the cell group 112 is configured with four cells 111 electrically connected in series, and one cell control unit 121 monitors the four cells 111.

Figure 2 is a diagram showing the circuit configuration of the cell control unit 121. The cell control unit 121 includes a voltage detection circuit 122, a control circuit 123, a signal input/output circuit 124, and a temperature detection unit 125. The voltage detection circuit 122 measures the terminal voltage of each cell 111. The temperature detection unit 125 measures the temperature of the cell group 112. The control circuit 123 receives the measurement results from the voltage detection circuit 122 and the temperature detection unit 125 and transmits them to the battery pack control unit 150 via the signal input/output circuit 124. The circuit configuration generally implemented in the cell control unit 121 to equalize voltage and SOC variations between the cells 111 that occur due to self-discharge, current consumption variations, etc. may use any existing technology.

The temperature detection unit 125 provided in the cell control unit 121 in Figure 2 has the function of measuring the temperature of the cell group 112. The temperature detection unit 125 measures one temperature for the cell group 112 as a whole and treats that temperature as a representative temperature value for the cells 111 that make up the cell group 112. The temperature measured by the temperature detection unit 125 is used for various calculations to detect the state of the cell 111, the cell group 112, or the battery pack 110. Figure 2 assumes this, so one temperature detection unit 125 is provided in the cell control unit 121. It is also possible to provide a temperature detection unit 125 for each cell 111 to measure the temperature of each cell 111 and perform various calculations based on the temperature of each cell 111; however, in this case, the number of temperature detection units 125 would increase, making the configuration of the cell control unit 121 more complex.

Figure 2 shows a simplified temperature detection unit 125. In reality, a temperature sensor is installed at the object to be measured, and the installed temperature sensor outputs temperature information as a voltage. The measurement result is sent to the signal input/output circuit 124 via the control circuit 123, and the signal input/output circuit 124 outputs the measurement result outside the cell control unit 121. The function that realizes this series of steps is implemented in the cell control unit 121 as the temperature detection unit 125, and the voltage detection circuit 122 can also be used to measure the temperature information (voltage).

The battery pack control unit 150 and the cell management unit 120 transmit and receive signals via the signal communication unit 160 via an isolation element 170 such as a photocoupler. The isolation element 170 is provided because the battery pack control unit 150 and the cell management unit 120 use different operating power sources. That is, the cell management unit 120 operates using power from the battery pack 110, while the battery pack control unit 150 uses a battery for on-board accessories (e.g., a 12V battery) as its power source. The isolation element 170 may be mounted on the circuit board that constitutes the cell management unit 120, or on the circuit board that constitutes the battery pack control unit 150. Depending on the system configuration, the isolation element 170 may be omitted.

The communication unit between the battery pack control unit 150 and the cell control units 121a and 121b in this embodiment will be described. The cell control units 121a and 121b are connected in series in descending order of potential of the cell groups 112a and 112b that they monitor. Signals sent by the battery pack control unit 150 are input to the cell control unit 121a by the signal communication unit 160 via an insulating element 170. The output of the cell control unit 121a and the input of the cell control unit 121b are also connected by the signal communication unit 160 for signal transmission. Note that in this embodiment, the cell control units 121a and 121b are not connected via the insulating element 170, but the insulating element 170 may be used. The output of the cell control unit 121b is then transmitted by the signal communication unit 160 via the insulating element 170 and the input of the battery pack control unit 150. In this way, the battery pack control unit 150 and the cell control units 121a and 121b are connected in a loop by the signal communication unit 160. This loop connection is also called a daisy chain connection, a string of beads connection, or a root-and-root connection.

The configuration of the battery pack control unit 150 will be explained based on Figure 3. In this embodiment, for simplicity, explanations of the diagnostic results for the cells 111 and the processing based on the abnormal signal output when a communication error occurs in the cell management unit 120 will be omitted. The battery pack control unit 150 is composed of an SOC calculation unit 151, an SOH calculation unit 152, a model voltage calculation unit 153, a correction coefficient calculation unit 154, and a power limit value calculation unit 155.

The SOC calculation unit 151 receives as input the average voltage of each cell 111 constituting the battery pack 110, the current flowing through the battery pack 110, and model parameters output by the model voltage calculation unit 153 (described later), and outputs the SOC and SOCv. The details of the calculation process for the SOC and SOCv will be described later. The SOH calculation unit 152 receives as input the SOC and SOCv output by the SOC calculation unit 151 and the model parameters output by the model voltage calculation unit 153, and calculates and outputs the SOH, which indicates the battery deterioration rate. The model voltage calculation unit 153 receives as input the current, temperature, SOC, and SOH, and outputs various model parameters and the battery voltage. The SOC is obtained as a calculation result by the SOC calculation unit 151. The SOH is obtained as a calculation result by the SOH calculation unit 152. The various model parameters are parameters that constitute a voltage equivalent circuit model that predicts the battery voltage. The voltage output by the model voltage calculation unit 153 includes the model voltage and OCV. The correction coefficient calculation unit 154 executes a correction coefficient calculation step. The correction coefficient calculation step is a step in which the battery voltage measurement value, the model voltage calculated by the model voltage calculation unit 153, and the OCV are input, and a correction coefficient k is calculated and output. The power limit value calculation unit 155 executes a power limit value calculation step. The power limit value calculation step is a step in which the model parameters (Ro, Rp, τ, and Vp, described below) calculated by the model voltage calculation unit 153, the OCV, and the correction coefficient k are input, and the maximum input power (Pmax_c) and the maximum output power (Pmax_d) are output.

The memory unit 180 stores information such as the internal resistance characteristics of the battery pack 110, the cell 111, and the cell group 112, the capacity at full charge, the polarization resistance characteristics, the degradation characteristics, the individual difference information, and the correspondence between SOC and OCV. In this embodiment, the memory unit 180 is configured to be installed outside the battery pack control unit 150 or the cell management unit 120, but the battery pack control unit 150 or the cell management unit 120 may be configured to have a memory unit that stores the above information.

Figure 4 is a diagram showing an example of an SOC table stored in memory unit 180. The SOC table is a data table that describes the correspondence between the OCV of the battery cell 111 and the SOC of the battery cell 111 according to temperature. Memory unit 180 also stores various battery characteristic information, such as internal resistance characteristics and polarization resistance characteristics, as a data table that describes the correspondence with various parameters such as SOC and temperature, similar to the SOC table. Note that while a data table is used in the description of this embodiment, the correspondence between OCV and SOC may also be expressed using a formula or the like, and is not limited to the form of a data table.

The SOC calculation unit 151 constituting the battery pack control unit 150 will be described using Figures 5 and 6. The SOC calculation unit 151 is composed of an SOCi calculation unit 151-1, an SOCv calculation unit 151-2, and a combination calculation unit 151-3. The SOCi calculation unit 151-1 receives the current and the previous value of the SOC calculation result (the calculation result from one cycle ago) output by the combination calculation unit 151-3 as input, and calculates and outputs an SOC (hereinafter referred to as SOCi) based on the integrated value of the current. The SOCv calculation unit calculates the OCV based on the battery voltage, current, and temperature, and calculates an SOC (hereinafter referred to as SOCv) based on the correspondence relationship between OCV and SOC shown in Figure 6. The combination calculation unit 151-3 receives SOCi and SOCv as input, and outputs a weighted average of SOCi and SOCv.

Next, the SOCi calculation unit 151-1 will be described. SOCi is calculated by adding the amount of change in SOC due to the current flow to the previous value (the calculation result from one cycle ago) of the result output by the combination calculation unit 151-3 (Equation (1)).
Here, SOC_old is the previous value of SOC (the calculation result from one cycle ago) obtained by equation (4) described later, I is the current, Qmax is the full charge capacity of the single battery 111, and ts is the control period (the sampling period for current, voltage, etc.).

The SOCv calculation unit 151-2 will now be described. The SOCv calculation unit 151-2 receives as input the battery's voltage, current, and model parameters (here, Ro and Vp, which will be described later; of the model parameters in FIG. 5, only Ro and Vp, which are used for SOC calculation, are extracted and used as input), calculates the battery's OCV, and estimates the SOCv from the correspondence relationship between SOC and OCV shown in FIG. 6. The OCV is calculated based on a voltage equivalent circuit such as that shown in FIG. 7 (details will be described later). According to the equivalent circuit in FIG. 7, the battery's OCV can be expressed by the following equation (2).

The combination calculation unit 151-3 receives the SOCi calculated by the SOCi calculation unit 151-1, the SOCv calculated by the SOCv calculation unit 151-2, the current, and the temperature as inputs, and calculates the SOC based on the following equation (3).
Here, w represents a weighting coefficient, which is calculated, for example, from the following equation (4).
According to equation (4), when the current is large, w becomes small, so the degree of bias toward SOCi becomes high, and conversely, when the current is small, w becomes large, so the degree of bias toward SOCv becomes high. In this embodiment, to avoid the influence of SOCv error due to resistance error when current is flowing, a weighting coefficient such as that in equation (4) is set, but the present invention is not limited to this.

Next, the SOH calculation unit 152 will be described with reference to Figure 7. The SOH calculation in this embodiment is a method of extracting and correcting the difference between the input SOC and the SOCv calculated using the internal resistance Ro as an error in Ro (change in Ro due to deterioration).

The SOH calculation unit 152 has a calculation execution determination unit 152-1, an internal resistance correction unit 152-2, and an SOH calculation unit 152-3. The calculation execution determination unit 152-1 determines whether or not to execute SOH calculation based on the SOC, SOCv, current, and temperature. The internal resistance correction unit 152-2 corrects Ro, one of the model parameters (only Ro used in SOH calculation is extracted and utilized from the model parameters), based on the determination result of the calculation execution determination unit 152-1. The SOH calculation unit 152-3 inputs the SOC, temperature, and corrected Ro (Ro') and calculates the ratio to the initial Ro. Details of these processing units will be explained below.

The calculation execution determination unit 152-1 inputs the SOC, SOCv, current, and temperature and determines whether to perform an internal resistance correction calculation. Specifically, it checks whether the SOC, current, temperature, and current flow time are within a specified range, and if all conditions are met, it determines that calculation is possible and outputs the determination result. The ranges of SOC, current, temperature, and current flow time are determined taking into account the battery characteristics, whether the voltage behavior is in a range that can be predicted using a battery equivalent circuit model such as that shown in Figure 8 (described below) (whether charging or discharging is occurring in a range that cannot be reproduced by the equivalent circuit model), and the effects of SOC error and current and temperature sensor errors. If the calculation execution determination unit 152-1 determines that calculation is possible, it compares the SOC and SOCv to determine whether Ro needs to be corrected and the direction of correction.

The internal resistance correction unit 152-2 corrects the input Ro when the calculation execution determination unit 152-1 determines that correction is necessary. Specifically, if correction is determined to be necessary and the resistance value needs to be corrected lower, a predetermined value is subtracted from Ro. Conversely, if the resistance value needs to be corrected higher, a predetermined value is added to Ro.

The SOH calculation unit 152-3 calculates the initial Ro (internal resistance value RoInit when new) based on Ro' calculated by the internal resistance correction unit 152-2 and the input SOC and temperature, and calculates the rate of increase of Ro based on the following equation (5).
If it is determined that the internal resistance calculation cannot be performed based on the result of the determination by the calculation execution determination unit 152-1, the internal resistance value is not corrected, that is, the internal resistance value of one calculation cycle before is output. For example, when calculation processing is performed according to an arbitrary calculation cycle, the internal resistance value of the calculation cycle one cycle before the calculation cycle in which it was determined that the calculation cannot be performed is output.

Next, the model voltage calculation unit 153 that constitutes the battery pack control unit 150 will be explained using Figures 8 and 9.

Figure 8 shows a voltage equivalent circuit model that reproduces the battery voltage. The equivalent circuit model shown in this figure is configured by connecting the internal resistance Ro and a parallel circuit of Rp and C in series with respect to the electromotive force component representing the battery's open circuit voltage (OCV). The internal resistance Ro is a resistance component resulting from the battery's components, such as the electrodes and electrolyte, and is time-independent. The parallel circuit of Rp and C simulates the internal resistance component associated with the battery's electrochemical reaction. Hereinafter, Rp will be referred to as the polarization resistance, and the time constant τ (= Rp × C) in the parallel circuit will be referred to as the polarization time constant. In this equivalent circuit model, the battery voltage, or CCV, is calculated using the following equation (6). Vp_z in equation (6) represents the polarization voltage from one calculation cycle ago.

The model parameters in the equivalent circuit model, OCV, Ro, Rp, and τ, can be extracted from the voltage waveform when the battery is charged or discharged. Figure 9 shows the voltage waveform when a constant charging current is input to the battery. As shown in Figure 9, the moment the charging current is input, a voltage change (Vo) occurs corresponding to Ro, the time-independent internal resistance component of the OCV. This is followed by the polarization voltage Vp, a voltage component that changes over time with the time constant τ. After charging is completed, the voltage change corresponding to Vo becomes zero, and the polarization voltage Vp gradually relaxes with the time constant τ, ultimately resulting in the battery voltage approaching the OCV. Such experiments were conducted at various SOCs, temperatures, charging, and discharging conditions. The voltage before the start of charging and discharging was extracted as the OCV. Then, Ro, Rp, and τ were extracted using, for example, the least-squares method to reproduce the voltage changes under each condition. A database was then constructed and stored as a map in the memory unit 180.

In this embodiment, the model voltage calculation unit 153 stores in the storage unit 180 the pre-extracted OCV for each SOC and temperature, an Ro map (RoInitMap) for a new battery, an Rp map (RpInitMap) for a new battery, and a τ map (τMap), and calculates and outputs model parameters such as Ro, Rp, τ, and Vp corresponding to the SOC, SOH, and temperature, as well as the model voltage CCV, using the SOC, SOH, and temperature as inputs. The model parameters are calculated using the following equation (7). The model voltage CCV is calculated using the above equation (6).

Next, the correction coefficient calculation unit 154 in this embodiment will be described with reference to Figures 10 and 11. Figure 10, like Figure 9, shows the voltage waveform when a constant square-wave current is input to the battery, representing a large current and continuous, long-term current application. The solid line represents the battery voltage waveform of the actual battery, and the dotted line represents the voltage waveform calculated using the equivalent circuit model described in Figure 8. While the solid and dotted lines closely match in the short-current application period, the discrepancy increases over time. In the latter half of discharge, the behavior of the actual battery (shown by the solid line) exhibits a significant curvature, revealing a significant deviation from the model voltage. The significant curvature in the voltage behavior during long-term current application is due to the increase in the internal resistance component contributing to the diffusion of lithium ions within the battery as the lithium ions at the electrode-electrolyte interface decrease. This behavior cannot be reproduced by the equivalent circuit model shown in Figure 8, resulting in the significant deviation in the voltage behavior during the latter half of discharge.

When a battery is charged or discharged in a situation where there is a large discrepancy in voltage (resistance) behavior, the available input/output power described below cannot be accurately calculated, which could result in deviation from the upper and lower voltage limits that must be observed. To solve this problem, one approach is to construct an equivalent circuit model of voltage that can be reproduced, including the region where the voltage bends, as shown in Figure 10, but modeling such a region is generally very difficult. Therefore, in order to more accurately calculate the available input/output power even when charging or discharging in a region that cannot be reproduced by a voltage model, this example describes a method of calculating a correction coefficient based on the actual measured voltage and model voltage, and reflecting this in the calculation of the available input/output power.

An example of a method for calculating the correction coefficient in this embodiment is shown in Fig. 11. In this embodiment, the voltage change due to the internal resistance is calculated from the model voltage and the actually measured voltage, and the ratio between these is extracted as the correction coefficient (Equation (8)).
In equation (8), CCVmeas represents the measured voltage, and CCVCalc represents the model voltage. The difference between OCV and CCV represents the voltage change due to internal resistance, and the ratio of the voltage change calculated from the measured voltage (measured voltage - OCV in Figure 11) to the voltage change calculated from the model voltage (model voltage - OCV) represents how many times the actual internal resistance of the battery is compared to the internal resistance calculated by the voltage model. The result of this calculation is the correction coefficient k in Figure 11. The correction coefficient calculation unit 154 calculates the correction coefficient k according to equation (8) and outputs it to the power limit value calculation unit 155, which will be described later.

The power limit value calculation unit 155 will be described with reference to Figure 12. The power limit value calculation unit 155 inputs the time-dependent polarization resistance Rp and polarization voltage Vp, which are model parameters, and the correction coefficient k calculated by the correction coefficient calculation unit 154. The power limit value calculation unit 155 has a correction coefficient reflection unit 155-1, an allowable current calculation unit 155-2, and an allowable power calculation unit 155-3. The correction coefficient reflection unit 155-1 corrects Rp and Vp. The allowable current calculation unit 155-2 inputs the OCV and model parameters, including the parameters corrected by the correction coefficient reflection unit 155-1, and calculates the maximum current Imax_c that can be input to the battery and the maximum current Imax_d that can be output. The allowable power calculation unit 155-3 receives as input the OCV, model parameters including the parameters corrected by the correction coefficient reflection unit 155-1, Imax_c, and Imax_d, and calculates and outputs the maximum power Pmax_c that can be input and the maximum power Pmax_d that can be output.

The correction coefficient reflection unit 155-1 uses the input correction coefficient k to correct the model parameters used in calculating Imax_c, Imax_d, Pmax_c, and Pmax_d. Because the correction coefficient k is a coefficient that reflects the influence of the polarization component that changes over time, Ro, which is a resistance component that is not time-dependent, is excluded from the correction target, and the correction coefficient k is used to correct only the polarization resistance Rp and the polarization voltage Vp. In this embodiment, the polarization resistance Rp and the polarization voltage Vp are corrected using the following equation (9).

The allowable current calculation unit 155-2 uses the model parameters including Rp and Vp corrected by equation (9) and the OCV as input, and calculates the maximum current Imax_c that can be input to the battery and the maximum current Imax_d that can be output using the following equations (10) and (11).
Here, in equations (10) and (11), tcont represents the expected number of seconds (sec) of continuous current flow, Ilimit represents the upper limit current value determined in consideration of the resistance of components of the battery system, such as relays and fuses, Vmax represents the upper limit voltage, and Vmin represents the lower limit voltage. The expected number of seconds of continuous current flow is the number of seconds set when specifying the current and power that can be continuously flowed for a predetermined number of seconds. For example, to calculate the current or power that can be continuously flowed for 5 seconds, tcont is set to 5.

Next, the allowable power calculation unit 155-3 receives as input the model parameters including Rp and Vp corrected by equation (9) and Imax_c and Imax_d calculated by the OCV and allowable current calculation unit 155-2, and calculates the maximum input power Pmax_c and the maximum output power Pmax_d using the following equations (12) and (13).
In equations (12) and (13), N represents the number of cells that make up the battery system.

The effects of the present invention will be explained using Figures 13 and 14. Figures 13 and 14 show the waveforms of power, current, and voltage when the battery is discharged according to the available output power that is updated every calculation cycle. Figure 13 shows the waveforms before the application of the present invention, and Figure 14 shows the waveforms after the application of the present invention.

First, let's look at Figure 13, which shows the state before the present invention was applied. Discharge begins from a resting state with a power equivalent to the available output power calculated using equation (13). As the discharge progresses, current flows, resulting in a decrease in SOC, gradually decreasing the available discharge power. As the current continues to flow, the voltage decreases over time. However, at some point, an error occurs in the region where the lithium ion diffusion resistance increases, which cannot be reproduced using the battery voltage equivalent circuit model used to calculate the available output power. This results in the actual measured voltage being lower than the model voltage, i.e., the internal resistance is high. In this situation, the internal resistance calculated for the available output power should be increased, i.e., the available output power should be calculated to be lower. However, before the present invention was applied, the difference between the actual measured voltage and the model voltage was not reflected in the available output power calculation, resulting in excessive power being input, resulting in the voltage falling below the lower limit.

On the other hand, in Figure 14, which shows similar test results when the present invention is applied, the correction coefficient k is calculated from the model voltage and the actual measured voltage and reflected in the available output power, so that the power is corrected to a smaller value from the point at which a deviation occurs between the model voltage and the actual measured voltage, and as a result, discharge continues without deviating from the lower limit voltage.

According to this embodiment, by reflecting the correction coefficient k based on the actual measured voltage and model voltage in the calculation of the available input/output power, it is possible to calculate the available input/output power that can prevent deviation from the upper and lower limit voltages due to modeling errors in the voltage equivalent circuit model of the secondary battery.

Note that Figure 14 explains the effects of Example 1 using the example of a charge/discharge test in which power equivalent to the available output power is input, but similar effects can be expected when inputting power equivalent to the available input power. In other words, once a deviation occurs between the model voltage and the measured voltage, a correction is made to reduce the power, making it possible to continue charging without exceeding the upper voltage limit.

In this embodiment, the correction coefficient is calculated as the ratio of the difference between the OCV and the model voltage and the measured voltage, as shown in equation (8). However, this is not a limitation. A simpler configuration would be to create a correction coefficient map in advance, with the difference between the model voltage and OCV (model voltage difference) and the difference between the measured voltage and OCV (measured voltage difference) as axes, and input the model voltage difference and the measured voltage difference during charging and discharging to this map to output the correction coefficient. Alternatively, the calculated polarization voltage Vp (Vp_model) based on the equivalent circuit model shown in Figure 8 and the measured-value-based polarization voltage Vp (Vp_measure), calculated by subtracting the OCV and Vo from the measured voltage, could be directly extracted as resistance components that change over time, and the correction coefficient could be calculated as the ratio of these. Any indicator that indicates the deviation of the internal resistance component would be acceptable.

A second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, a correction coefficient k corresponding to the difference between the measured voltage and the model voltage is calculated using equation (8), and the calculated correction coefficient k is used to correct the resistance component over time as shown in equation (9), thereby calculating the input and output available power.

However, as shown in Figure 1, the battery 100, which is a battery system, is composed of an assembled battery 110 in which cells 111 are connected in series, and the battery voltage can vary due to individual differences between each cell 111 and temperature variations. The input and output power capacities must be calculated as the maximum power within a range in which the voltages of all cells 111 constituting the assembled battery 110 do not deviate from the upper and lower voltage limits. Therefore, this embodiment describes an example in which a correction coefficient is determined taking into account the voltage variations of each cell 111 and reflected in the calculation of the input and output power capacities, thereby calculating the input and output power capacities so that all cells 111 constituting the assembled battery 110 do not deviate from the upper and lower voltage limits.

In explaining this embodiment, we will focus on the differences from embodiment 1, and omit explanations of parts with configurations similar to embodiment 1.

The differences between this embodiment and embodiment 1 are the battery pack control unit 150', and the correction coefficient calculation unit 154' and power limit value calculation unit 155' in the battery pack control unit 150'.

First, the battery pack control unit 150' will be described with reference to Figure 15. The difference from the battery pack control unit 150 in Example 1 is that the highest voltage (maximum cell voltage) and the lowest voltage (minimum cell voltage) of the cells 111 that make up the battery pack 110 are input to the correction coefficient calculation unit 154', which outputs a total of three correction coefficients: a correction coefficient kchg for the available input current, a correction coefficient kdis for the available discharge current, and a voltage correction coefficient kvol, which are described below, and input them to the power limit value calculation unit 155'. The power limit value calculation unit 155' takes kchg, kdis, and kvol as inputs, and outputs the maximum available input power Pmax_c and the maximum available output power Pmax_d.

Next, the correction coefficient calculation unit 154' will be described. The difference from the correction coefficient calculation unit 154 in Example 1 is that the maximum cell voltage and minimum cell voltage are added to the input, the correction coefficient kchg for the inputtable current is calculated based on the maximum cell voltage and model voltage, the correction coefficient kdis for the dischargeable current is calculated based on the minimum cell voltage and model voltage, and the voltage correction coefficient kvol is calculated based on the average voltage and model voltage.

The maximum input current Imax_c needs to be set as a current value that prevents all of the cells 111 constituting the battery pack 110 from exceeding their upper limit voltages, so a correction coefficient is calculated and utilized based on the highest cell voltage, which is the highest voltage among all of the cells 111 constituting the battery pack 110. The formula for calculating kchg is shown in the following formula (14).

Similarly, the maximum output current Imax_d needs to be set as a current value that prevents all of the cells 111 constituting the battery pack 110 from deviating from the lower limit voltage, so a correction coefficient is calculated and utilized based on the minimum cell voltage, which is the lowest voltage among all of the cells 111 constituting the battery pack 110. The formula for calculating kdis is shown in the following formula (15).

Furthermore, the correction of the internal resistance component used to calculate the voltage when the inputtable current and the dischargeable current are applied, which are calculated when calculating the inputtable power and the dischargeable power, corresponds to the sum of the single cells 111 that make up the battery pack 110, so a correction coefficient is calculated and used based on the average voltage of the entire battery pack 110 (= total voltage ÷ number of cells). kvol is shown in the following equation (16).

Next, the power limit value calculation unit 155' will be described with reference to Figure 16. The difference from the power limit value calculation unit 155' in Example 1 is that the correction coefficients kchg, kdis, and kvol described in equations (14) to (16) are input, and these are used to calculate the allowable current (Imax_c, Imax_d) and allowable power (Pmax_c, Pmax_d). The internal resistance components used in calculating the allowable current (Imax_c, Imax_d) are corrected based on the correction coefficients kchg and kdis, and the results Rp_chg and Vp_chg and Rp_dis and Vp_dis are calculated and output to the allowable current calculation unit 155-2'. The internal resistance components used in calculating the allowable power (Pmax_c, Pmax_d) are corrected based on the correction coefficient kvol, and the results Rp_vol and Vp_vol are output to the allowable power calculation unit 155-3'. The allowable current calculation unit 155-2' and the allowable power calculation unit 155-3' perform the calculation processing described below based on their respective inputs.

The correction coefficient reflecting unit 155-1' will now be described. The correction coefficient reflecting unit 155-1' corrects the polarization resistance Rp and polarization voltage Vp, which are input as in the first embodiment, using correction coefficients kchg, kdis, and kvol. The inputtable current internal resistance Rp'_chg and polarization voltage Vp'_chg are calculated using kchg as shown in the following equation (17).
Similarly, the dischargeable current internal resistance Rp'_dis and the polarization voltage Vp'_dis are calculated using kdis as in the following equation (18).
Furthermore, the voltage calculation internal resistance Rp'_vol and the polarization voltage Vp'_vol are calculated using kvol as shown in the following equation (19).

The allowable current calculation unit 155-2' uses the model parameters including Rp and Vp corrected by equations (17) and (18) and the OCV as input, and calculates the maximum current Imax_c that can be input to the battery and the maximum current Imax_d that can be output using the following equations (20) and (21).
Here, tcont and Ilimit in equations (20) and (21) represent upper limit current values determined in consideration of the expected continuous current flow time and the resistance of components of the battery system, such as relays and fuses, as in the first embodiment.

Next, the allowable power calculation unit 155-3' receives as input the model parameters including Rp and Vp corrected by equation (19) and Imax_c and Imax_d calculated by the OCV and allowable current calculation unit 155-2', and calculates the maximum input power Pmax_c and the maximum output power Pmax_d using the following equations (22) and (23).
In the equations (22) and (23), N represents the number of cells that make up the battery system, as in the first embodiment.

The effects of the present invention will be explained using Figures 17 to 21. Figure 17 is a schematic diagram of a battery pack in which three cells 111 with different internal resistance values are connected in series. Figures 18 to 21 show the power, current, and voltage waveforms when the battery pack shown in Figure 17 is discharged or charged in accordance with the available output power or available input power that is updated every calculation cycle, similar to Figures 13 and 14 of Example 1. Figures 18 and 19 are graphs in which the correction coefficient is determined based on the average voltage, based on the content described in Example 1, and Figures 20 and 21 show the waveforms after applying the present invention to this example.

First, let us consider Figure 18. As in Example 1, discharge begins from a resting state with a power equivalent to the available output power. As the discharge progresses, current flows, resulting in a decrease in SOC, gradually decreasing the available discharge power. As the voltage continues to flow, it decreases over time. At some point, the voltage reaches a region where the lithium-ion diffusion resistance increases, a region that cannot be reproduced by the battery voltage equivalent circuit model used to calculate the available output power. The available output power is corrected by a correction coefficient corresponding to the difference between the average voltage of the three cells and the model voltage. While the average voltage continues to discharge at the lower limit, the lowest cell voltage drops significantly and deviates from the lower limit due to its higher internal resistance compared to the average internal resistance of the three cells. Similarly, Figure 19 shows an example of charging according to the available input power. While the average voltage does not deviate from the upper limit, the highest cell voltage, with its high internal resistance, deviates from the upper limit.

On the other hand, Figure 20 shows the results of a discharge test based on the available output power when this embodiment is applied. The correction coefficient kdis is calculated from the model voltage and the lowest cell voltage, and is reflected in the available output power. From the point at which a deviation occurs between the model voltage and the lowest cell voltage, the power is corrected to a smaller value. As a result, the voltages of all batteries, including the lowest cell voltage, continue to discharge without deviating from the lower limit voltage.

Furthermore, Figure 21 shows the results of a charging test using the available input power when this embodiment is applied. The correction coefficient kchg is calculated from the model voltage and the maximum cell voltage and reflected in the available input power. From the point at which a deviation occurs between the model voltage and the maximum cell voltage, the power is corrected to a smaller value. As a result, charging continues without the voltage of all batteries, including the maximum cell voltage, deviating from the upper limit voltage.

According to this embodiment, the correction coefficient kdis based on the lowest cell voltage and model voltage and the correction coefficient kvol based on the average voltage and model voltage are reflected in the calculation of available output power as correction coefficients for available output power, and the correction coefficient kchg based on the highest cell voltage and model voltage and the correction coefficient kvol based on the average voltage and model voltage are reflected in the calculation of available input power as correction coefficients for available input power, thereby making it possible to calculate available input/output power that can prevent the voltages of all batteries connected in series that make up the secondary battery system from deviating from the upper and lower voltage limits.

A third embodiment of the present invention will be described with reference to FIGS.
In the first and second embodiments, a correction coefficient is calculated according to the difference between the model voltage and the measured voltage, including the highest and lowest cell voltages, and the calculated correction coefficient k is used to correct the internal resistance component used in the calculation of the available input/output power. In this embodiment, a simpler method is described in which the available input/output power is directly limited to a smaller value when the correction coefficient exceeds a predetermined value, without correcting the internal resistance component.

In explaining this embodiment, we will focus on the differences from embodiments 1 and 2, and will omit explanations of parts with configurations similar to those of embodiments 1 and 2.

Figure 22 shows the functional configuration of the power limit value calculation unit 155'' in this embodiment. The difference from the power limit value calculation unit 155' in embodiment 2 (Figure 16) is that in the power limit value calculation unit 155' in embodiment 2, kchg, kdis, and kvol were input to the correction coefficient reflection unit 155-1', whereas in this embodiment, the correction coefficient reflection unit 155-1' has been removed and they are input to the allowable power limit unit 155-4, which is located after the allowable power calculation unit 155-3'.

The allowable power limiting unit 155-4 estimates the limit rate of the input/output power corresponding to the inputs kchg, kdis, and kvol, and reflects the estimated results in the outputs Wmax_c and Wmax_d of the allowable power calculation unit 155-3', outputting them as the final input/output power (Pmax_c and Pmax_d).

The method for calculating the limit rate will be described with reference to Figure 23. Figure 23 is a graph with the inputs kchg, kdis, and kvol on the horizontal axis and the limit coefficients a_chg, a_dis, and a_vol corresponding to the input values on the vertical axis. The input correction coefficient is set to 1 to start the limit, and the limit coefficient is set to 0 at the thresholds (kchg_end, kdis_end, kvol_end) where each correction coefficient is individually set. Figure 23 shows an example where the relationship between 1 and the thresholds (kchg_end, kdis_end, kvol_end) where the limit coefficient becomes 0 is linear, but this is not limited to this and it may be implemented as a map so that any value corresponding to the input value can be set.

As described in the second embodiment, there are correction coefficients (kchg, kdis) for calculating the input and dischargeable current and a correction coefficient (kvol) for the voltage when the input and dischargeable current are flowing. Therefore, in this embodiment, the smaller of a_chg corresponding to kchg and adis corresponding to kvol is used as the limit coefficient (ain) for the final inputable power, and the smaller of a_dis corresponding to kdis and kvol is used as the limit coefficient (aout) for the dischargeable power.

Based on the limiting coefficients calculated by the equations (24) and (25), Pmax_c and Pmax_d are calculated by the following equations (26) and (27).

The effects of the present invention will be described based on Figures 24 and 25. As with Example 2, Figure 24 shows the results of continuously inputting power equivalent to the available output power into the battery, while Figure 25 shows the results of continuously inputting power equivalent to the available input power into the battery. The graphs in Figures 24 and 25 each have time on the horizontal axis and, from the top, power, limit coefficient, and voltage on the vertical axis.

Looking at the graphs of limit coefficients and voltages in Figures 24 and 25, it can be seen that when a difference occurs between the model voltage and the maximum cell voltage shown in Figure 24, the limit coefficient becomes smaller than 1, and accordingly the output power is limited, reducing the power applied to the battery. Similarly, when a difference occurs between the maximum cell voltage shown in Figure 25 and the model voltage, the limit coefficient becomes smaller than 1, and accordingly the input power is limited, reducing the power applied to the battery. As a result, it was confirmed that in both the examples shown in Figures 24 and 25, it was possible to calculate the input/output power so that the voltages of all batteries connected in series did not exceed the upper or lower limit voltages.

According to this embodiment, the limit coefficients (ain, aout) for limiting the available input/output power are calculated based on the correction coefficients kdis, kchg, and kvol described in Example 2, and reflected in the available input/output power, thereby making it possible to calculate the available input/output power that can prevent the voltages of all series-connected batteries that make up the secondary battery system from deviating from the upper and lower voltage limits.

A fourth embodiment of the present invention will be described with reference to FIGS.
In the first, second, and third embodiments, a correction coefficient is calculated according to the difference between the model voltage and the measured voltage, including the highest and lowest cell voltages, and the input and output available power is calculated using the calculated correction coefficient k. In the fourth embodiment, the timing for reflecting the calculated correction coefficient will be described.

Typically, the battery pack control unit 150 includes a means for detecting changes in the battery's internal resistance due to deterioration (equivalent to the SOH calculation unit 152 in this invention). The means for detecting the battery's internal resistance sets calculation execution conditions to improve calculation accuracy. For example, in the calculation using the equivalent circuit model shown in Figure 8 as in this embodiment, calculation is performed under conditions where the equivalent circuit model can accurately calculate voltage behavior, such as when the current flow time is short. In the range where calculation is determined to be possible, the internal resistance can be estimated with high accuracy, and the model voltage and the measured voltage match. Therefore, if the calculation result of the internal resistance can be directly reflected in the input/output available power calculation, there is no need to perform the correction process described in Examples 1 and 2 of the present invention. Furthermore, if internal resistance detection and the correction process described in Examples 1 and 2 of the present invention are performed simultaneously, the internal resistance component used in the input/output available power calculation may fluctuate, potentially causing the input/output available power calculation result to exhibit unexpected behavior, such as oscillation.

Therefore, in this embodiment, we describe a method in which the correction coefficients described in embodiments 1 and 2 are reflected only when the internal resistance calculation is outside the feasible range, and in which the correction coefficients are not reflected in the internal resistance component used in the input/output available power calculation within the feasible range.

In explaining this embodiment, we will focus on the differences from embodiments 1, 2, and 3, and will omit explanations of parts with configurations similar to embodiments 1, 2, and 3.

Figure 26 shows the battery pack control unit 150''' in this embodiment. The difference from the battery pack control unit 150' (Figure 15) in Example 2 is that the judgment result of the SOH calculation unit 152'' is output to the power limit value calculation unit 155'.

The SOH calculation unit 152'' in this embodiment will be described with reference to Figure 27. The only difference from embodiments 1 to 3 is that the determination result output by the calculation execution determination unit 152-1 is output to the outside of the SOH calculation unit 152''. The determination result is a determination result as to whether or not the internal resistance can be corrected and the SOH can be calculated.

Next, the power limit value calculation unit 155'' in this embodiment will be described with reference to Figure 28. The difference from embodiments 1 to 3 is that the judgment result, which is a new input to the power limit value calculation unit 155'', is added to the input of the correction coefficient reflection unit 155-1''. The correction coefficient reflection unit 155-1'' calculates the output parameters (Rp'_chg, Vp'_chg, Rp'_dis, Vp'_dis, Rp'_vol, Vp'_vol) according to the judgment result, using the following equations (28) and (29).

Case 1) When the judgment result is OK (SOH calculation can be performed)
In Case 1), the SOH calculation is performed and Rp and Vp are determined based on the latest SOH, so it is determined that correction using the correction coefficient is unnecessary and correction is not performed.

Case 2) When the judgment result is NG (SOH calculation cannot be performed)
In case 2), the SOH calculation is not suitable for execution, that is, it is a region where an error occurs in the voltage equivalent circuit model itself. In this case, correction is performed using a correction coefficient.

Furthermore, even when utilizing the limiting coefficients ain and aout as in Example 3, in Case 1, ain and aout are set to "1", and in Case 2, ain and aout calculated using the method described in Example 3 are applied.

The effects of this embodiment will be described with reference to Figures 29 and 30. From the top, Figures 29 and 30 each show waveforms of current, voltage, SOH, correction coefficient kchg, and maximum output power Pmax_d over time. Figure 29 shows the waveforms before this embodiment is applied, and Figure 30 shows the waveforms after this embodiment is applied.

Figures 29 and 30 both assume that the SOH is updated when current has been applied for a predetermined number of seconds after the current value is input. While the SOH calculation is being updated, the model voltage is also updated at the same time. Since the SOH calculation can fluctuate due to measurement errors (noise) in current, voltage, etc., in the section in the figure where SOH calculation is ON, the SOH will be updated while oscillating. Due to this influence, it is thought that the difference between the model voltage updated in the model voltage calculation unit 153, which uses SOH as input, and the actual measured voltage will also oscillate, and as a result, the correction coefficient kchg will also oscillate.

Before this embodiment was applied, the two oscillating components of SOH and kchg were reflected in Pmax_c, so as shown in Figure 29, the calculated values of both were affected by vibrations, causing the value of Pmax_c to fluctuate. However, when this embodiment is applied, the reflection of kchg is stopped while the SOH calculation is running, so the value is not affected by fluctuations in kchg. As a result, the behavior of Pmax_d can be calculated to be more stable than the waveform before this embodiment was applied.

Note that Figures 29 and 30 describe the available output power, but similar effects are expected for the available input power as well.

According to this embodiment, while the SOH calculation is operating, only the resistance estimate value in the battery's equivalent circuit model is utilized, and the correction coefficient described in embodiments 1 to 3 is not utilized. Correction of the input/output available power using the correction coefficient is applied only while the SOH calculation is not operating, thereby suppressing fluctuations in the input/output available power, and in conditions where the SOH calculation is not operating and resistance estimation using the equivalent circuit model is difficult (for example, when current is applied for a long period of time), it is possible to calculate the input/output available power that avoids deviation from the upper and lower limit voltages.

In addition, the input/output available power is a factor that affects the vehicle's driving control, and fluctuations in the input/output available power have a negative impact on the user's vehicle operability (drivability).Therefore, by applying this embodiment, suppressing fluctuations in the input/output available power can be expected to have the effect of improving the user's vehicle operability.

In this embodiment, an example has been shown in which the result of determining whether or not the SOH calculation can be performed is applied to whether or not the correction coefficient needs to be reflected. However, without using the output from the SOH calculation unit 152'', a means for independently determining whether or not the correction coefficient needs to be reflected may be provided within the power limit value calculation unit 155', and the correction coefficient may be reflected only under various conditions, such as when current is applied for a long period of time, when the current value is high, or when the difference between the actual voltage and the OCV is large.

As described above, the disclosed battery control device includes a correction coefficient calculation unit 154 that calculates a correction coefficient based on the discrepancy between the state of the secondary battery calculated from measured values related to the secondary battery and the state of the secondary battery calculated using a model related to the secondary battery, and a power limit value calculation unit 155 that calculates a value related to the power that can be input and output to the secondary battery by applying correction using the correction coefficient.
As a result, even if the actual power consumption deviates from the model prediction due to factors such as the application of a large current for a long period of time, the battery's available input and output power can be calculated with high accuracy, preventing the battery voltage from deviating from the upper and lower voltage limits and maximizing the battery's input and output performance, contributing to ensuring the reliability and efficient use of the battery system.

In addition, in the disclosed battery control device, the state of the secondary battery calculated from measured values related to the secondary battery is a voltage change in internal resistance based on an actual measured voltage obtained by measuring the voltage of the secondary battery, and the state of the secondary battery calculated using a model related to the secondary battery is a voltage change in internal resistance based on a model voltage obtained using a voltage equivalent circuit model of the secondary battery, and the correction coefficient calculation unit calculates the correction coefficient as the ratio between the voltage change in internal resistance based on the actual measured voltage and the voltage change in internal resistance based on the model voltage.
In the battery control device, the power limit value calculation unit corrects, using the correction coefficient, model parameters used to calculate the current and/or power that can be input and output by the secondary battery.
Therefore, it is possible to easily obtain a correction coefficient based on the actually measured voltage, correct the model parameters, and calculate the current and power that can be input and output.

In addition, the power limit value calculation unit corrects, among the model parameters, a resistance component having time dependency in the voltage equivalent circuit model of the secondary battery and a polarization voltage in the voltage equivalent circuit model of the secondary battery using the correction coefficient.
In this way, by selectively correcting factors that are affected by the long-term application of a large current, it is possible to improve the accuracy of calculation of the available input/output power.

Furthermore, a correction coefficient map may be constructed in advance that indicates the relationship between a measured voltage difference, which is the difference between the measured voltage and open circuit voltage of the secondary battery, a model voltage difference, which is the difference between a model voltage and the open circuit voltage of the secondary battery, and the correction coefficient, and the correction coefficient calculation unit may refer to the correction coefficient map based on the model voltage difference and the measured voltage difference during charging and discharging, to identify the correction coefficient.
The correction coefficient calculation unit may calculate the correction coefficient as a ratio between a polarization voltage calculated based on a voltage equivalent circuit model of the secondary battery and a polarization voltage calculated by subtracting an open circuit voltage and a voltage change due to a resistance that does not depend on time from an actually measured voltage.
In this way, the correction coefficient can be determined using any method.

Furthermore, the correction coefficient calculation unit determines the correction coefficient to be used in calculating the inputtable current and/or power, using the highest voltage among the voltages of the secondary batteries that are connected in series to form a battery pack as the actually measured voltage.
Furthermore, the correction coefficient calculation unit determines the correction coefficient to be used in calculating the outputtable current and/or power, using the lowest voltage among the voltages of the secondary batteries that are connected in series to form a battery pack as the actually measured voltage.
Therefore, it is possible to calculate the input and output power that will not deviate from the upper and lower limit voltages of all the cells that make up the battery pack.

In addition, the power limit value calculation unit can calculate a limit coefficient that limits the current and/or power that can be input and output to the secondary battery based on the correction coefficient, and limit the current and/or power that can be input and output to the secondary battery so that they are small.
In this way, by directly limiting the current and/or power that can be input and output to and from the secondary battery, the current and power that can be input and output can be calculated with a low load.

In addition, the disclosed battery control device further includes a SOH calculation unit 152 as a deterioration rate calculation unit that calculates the deterioration rate of the internal resistance of the secondary battery based on the current, voltage, and temperature flowing through the secondary battery, and the deterioration rate calculation unit determines that calculation of the deterioration rate can be performed when conditions for accurately calculating the deterioration rate are met, and the power limit value calculation unit suppresses correction using the correction coefficient when the deterioration rate calculation unit determines that calculation of the deterioration rate can be performed.
The deterioration rate calculation unit determines whether or not calculation of the deterioration rate can be performed based on a condition based on at least one of the charging rate, temperature, current, and current flow time of the secondary battery.
This prevents the deterioration rate calculation from affecting the correction rate, and allows an appropriate correction rate to be determined stably.

The above description is merely an example, and the present invention is in no way limited to the configuration of the above-mentioned embodiment. Furthermore, the above-mentioned embodiments can be used in any combination. Furthermore, while various embodiments and variations have been described above, the present invention is not limited to these. Other embodiments conceivable within the technical scope of the present invention are also included within the scope of the present invention.

For example, in each of the above-described embodiments, examples have been described in which a lithium-ion battery is used as the secondary battery, but similar charge/discharge control is possible when other secondary batteries are used. Furthermore, the present invention is not limited to secondary batteries for electric vehicles, but can be applied to secondary batteries for any purpose.

100... battery, 110... assembled battery, 111... cell, 112... cell group, 120... cell management unit, 121... cell control unit (monitoring four cells 111), 122... voltage detection circuit, 123... control circuit, 124... signal input/output circuit, 125... temperature detection unit, 130... current detection unit, 140... voltage detection unit, 150... assembled battery control unit, 151... SOC calculation unit, 151-1... SOCi calculation unit, 151-2... SOCv calculation unit, 151-3... combination calculation unit, 152... SOH calculation unit, 152 -1...calculation execution determination unit, 152-2...internal resistance correction unit, 152-3...SOH calculation unit, 152-4...power application time measurement unit, 153...model voltage calculation unit, 154...correction coefficient calculation unit, 155...power limit value calculation unit, 155-1...correction coefficient reflection unit, 155-2...allowable current calculation unit, 155-3...allowable power calculation unit, 155-4...allowable power limit unit, 180...storage unit, 200...vehicle control unit, 300, 310...relay, 400...inverter, 410...motor, 420...motor/inverter control unit

Claims (11)

a correction coefficient calculation unit that calculates a correction coefficient based on a difference between a state of the secondary battery calculated from measurements of the secondary battery and a state of the secondary battery calculated using a model of the secondary battery;
a power limit value calculation unit that calculates a value related to the power that can be input/output to/from the secondary battery by applying correction using the correction coefficient ;
the state of the secondary battery determined from the measurement value of the secondary battery is a voltage change of an internal resistance based on an actual measured voltage determined by measuring a voltage of the secondary battery;
the state of the secondary battery calculated using the model related to the secondary battery is a voltage change of an internal resistance based on a model voltage obtained using a voltage equivalent circuit model of the secondary battery;
The battery control device according to claim 1, wherein the correction coefficient calculation unit calculates, as the correction coefficient, a ratio between a voltage change in internal resistance based on the actually measured voltage and a voltage change in internal resistance based on the model voltage . The battery control device described in claim 1, characterized in that the power limit value calculation unit corrects model parameters used to calculate the current and/or power that can be input and output by the secondary battery using the correction coefficient. 3. The battery control device according to claim 2, wherein the power limit value calculation unit corrects, among the model parameters, a resistance component having time dependency in a voltage equivalent circuit model of the secondary battery and a polarization voltage in the voltage equivalent circuit model of the secondary battery using the correction coefficient. a correction coefficient calculation unit that calculates a correction coefficient based on a difference between a state of the secondary battery calculated from measurements of the secondary battery and a state of the secondary battery calculated using a model of the secondary battery;
a power limit value calculation unit that calculates a value related to the power that can be input/output to/from the secondary battery by applying correction using the correction coefficient;
Equipped with
constructing in advance a correction coefficient map showing a relationship between an actual measurement voltage difference, which is a difference between an actual measurement voltage and an open circuit voltage of the secondary battery, a model voltage difference, which is a difference between a model voltage and the open circuit voltage of the secondary battery, and the correction coefficient;
The battery control device according to claim 1, wherein the correction coefficient calculation unit refers to the correction coefficient map based on the model voltage difference and the measured voltage difference during charging and discharging, and specifies the correction coefficient. a correction coefficient calculation unit that calculates a correction coefficient based on a difference between a state of the secondary battery calculated from measurements of the secondary battery and a state of the secondary battery calculated using a model of the secondary battery;
a power limit value calculation unit that calculates a value related to the power that can be input/output to/from the secondary battery by applying correction using the correction coefficient;
Equipped with
the correction coefficient calculation unit calculates the correction coefficient as a ratio between a polarization voltage calculated based on a voltage equivalent circuit model of the secondary battery and a polarization voltage calculated by subtracting an open circuit voltage and a voltage change due to time-independent resistance from an actually measured voltage. 2. The battery control device according to claim 1, wherein the correction coefficient calculation unit determines the correction coefficient to be used in calculating the inputtable current and/or power by using the highest voltage of the plurality of secondary batteries that are connected in series to form a battery pack as the actually measured voltage. 2. The battery control device according to claim 1, wherein the correction coefficient calculation unit determines the correction coefficient to be used in calculating the outputtable current and/or power by using the lowest voltage among the voltages of the plurality of secondary batteries connected in series to form a battery pack as the actually measured voltage. The battery control device described in claim 1, characterized in that the power limit value calculation unit calculates a limit coefficient that limits the current and/or power that can be input and output to the secondary battery based on the correction coefficient, and limits the current and/or power that can be input and output to the secondary battery so that they are small. a correction coefficient calculation unit that calculates a correction coefficient based on a difference between a state of the secondary battery calculated from measurements of the secondary battery and a state of the secondary battery calculated using a model of the secondary battery;
a power limit value calculation unit that calculates a value related to the power that can be input/output to/from the secondary battery by applying correction using the correction coefficient;
Equipped with
a deterioration rate calculation unit that calculates a deterioration rate of an internal resistance of the secondary battery based on a current, a voltage, and a temperature flowing through the secondary battery;
the deterioration rate calculation unit determines that calculation of the deterioration rate is executable when a condition for accurately calculating the deterioration rate is met;
The battery control device according to claim 1, wherein the power limit value calculation unit suppresses the correction using the correction coefficient when the deterioration rate calculation unit determines that the calculation of the deterioration rate can be performed. 10. The battery control device according to claim 9, wherein the deterioration rate calculation unit determines whether or not calculation of the deterioration rate can be performed based on conditions based on at least one of the charging rate, temperature, current, and current flow time of the secondary battery. The battery control device
a correction coefficient calculation step of calculating a correction coefficient based on a difference between a state of the secondary battery calculated from measurements of the secondary battery and a state of the secondary battery calculated using a model of the secondary battery;
a power limit value calculation step of calculating a value related to the power that can be input/output to/from the secondary battery by applying correction using the correction coefficient ;
the state of the secondary battery determined from the measurement value of the secondary battery is a voltage change of an internal resistance based on an actual measured voltage determined by measuring a voltage of the secondary battery;
the state of the secondary battery calculated using the model related to the secondary battery is a voltage change of an internal resistance based on a model voltage obtained using a voltage equivalent circuit model of the secondary battery;
The battery control method according to the present invention, wherein the correction coefficient calculation step obtains, as the correction coefficient, a ratio between a voltage change in internal resistance based on the actually measured voltage and a voltage change in internal resistance based on the model voltage .